Any discussion of the related art throughout this specification should in no way be considered as an admission that such art is widely known or forms part of the common general knowledge in the field.
Antennas are attractive for many commercial and government applications. Antennas include a conductive material layer (a radiating structure) which can send and receive electromagnetic radiation by the acceleration of electrons. Sophisticated antenna technology and designs are required to control the transmitted pattern of said electromagnetic radiation. The geometry of the antenna can be controlled to focus the energy that is either transmitted or received by the antenna in a specific direction, i.e., the antenna's gain. Several important parameters (figures of merit) that are utilized for the design and application of antennas are radiation power density and intensity, directivity, beamwidth, efficiency, beam efficiency, bandwidth, polarization, and gain. Current antenna technology varies widely and the designs of modern antennas are specifically tailored depending on the figures of merit for the antenna application.
Microstrip antenna elements and arrays (sometimes termed microstrip patch antennas or printed antennas) are used within a plurality of electronic devices and systems and are well known to those skilled in the art. There exists an increasing demand for microstrip antenna elements and arrays of such elements in the design of a plurality of portable electronic devices—such as, but not limited to, GPS receivers, satellite radios, cellular telephones, and laptop computers. Microstrip antenna elements and arrays are favorable in such applications due to their low cost, low profile, low weight, high durability, and ease of fabrication as compared with other types of antenna structures. Microstrip antenna elements also can be easily fabricated to conform to a curved surface—such as, but not limited to, the nose cone of an aircraft or the interior of the shaped case of a portable electronic device. However, as the physical dimensions of a microstrip antenna element are inversely proportional to the resonant frequency of said element—that is, the size of the microstrip antenna will determine the “center frequency” at which the device is most sensitive—microstrip antennas are typically used to transmit and receive UHF frequencies and higher (that is, at frequencies greater than 300 MHz).
A typical microstrip antenna element is comprised of a plurality of coplanar layers, including a shaped conductive material layer which forms a radiating structure, an intermediate dielectric layer, and a ground plane layer. The radiating structure is formed of an electrically conductive material (such as, but not limited to, copper or gold) embedded or photoetched on the intermediate dielectric layer with a specific geometry and is generally exposed to free space. The microstrip antenna element generally radiates in a direction substantially perpendicular to the ground plane layer. However, arrays of microstrip antenna elements can be employed to achieve much higher gains and directivity than would be possible with a single microstrip antenna element.
FIG. 1A illustrates a typical rectangular microstrip antenna element. Rectangular microstrip antenna elements (as depicted in FIG. 1A) are most commonly used in electronic devices and systems, however microstrip antenna elements can be formed into any continuous shape as befits the needs of a specific application. The shape, physical dimensions, and orientation of a microstrip antenna element define parameters such as, but not limited to, resonant frequency, bandwidth, input impedance, and directivity. The design of microstrip antenna elements with respect to these parameters is well known to those skilled in the art.
Referring now to FIG. 1A, an insulating dielectric substrate layer 110 (with a layer height “H”) is deposited over a conductive layer 120. A shaped conductive trace 101 is further deposited over dielectric substrate layer 110. Shaped conductive trace 101 comprises a rectangular radiating structure 101a with a length “L,” a width “W,” and a thickness “T” and a transmission line element 101b. The conductive layer 120 forms a ground plane below the shaped conductive trace 101, with the dielectric substrate layer 110 providing electrical isolation between said ground plane and radiating structure 101a. 
FIG. 1B illustrates a typical rounded microstrip antenna element. As with the rectangular microstrip antenna element depicted in FIG. 1A, an insulating dielectric substrate layer 130 (with a layer height “H”) is deposited over a conductive layer 140. A shaped conductive trace 102 is further deposited over dielectric substrate layer 130. Shaped conductive trace 102 comprises a rounded radiating structure 102a with a thickness “T” and a transmission line element 102b. The conductive layer 140 forms a ground plane below the shaped conductive trace 102, with the dielectric substrate layer 130 providing electrical isolation between said ground plane and shaped radiating structure 102a. 
The height “H” of the dielectric substrate layer is typically not a critical design parameter, but in general the height “H” is limited to a dimension much smaller than the wavelength of operation. That is, H<<1/fc, where fc is the resonant (or center) frequency of the antenna element. The dielectric constant “∈r” (often termed permittivity by those skilled in the art) of the dielectric substrate layer (110 in FIG. 1A, 130 in FIG. 1B) is a more critical design parameter, as the degree to which the dielectric substrate layer (110 in FIG. 1A, 130 in FIG. 1B) impedes an electric field created between a radiating structure (101a in FIG. 1A, 102a in FIG. 1B) and a ground plane (conductive layer 120 in FIG. 1A, conductive layer 140 in FIG. 1B) will affect properties of the antenna element such as, but not limited to, resonant frequency and bandwidth. In some designs, an antenna element is simply suspended in open air above a ground plane in order to maximize the bandwidth of the microstrip antenna assembly. This, however, results in a device which is significantly more difficult to fabricate and less robust.
FIG. 2 is an electric field diagram illustrating the basic operation of a typical microstrip antenna element. An electric field is induced between radiating structure 201 (corresponding to rectangular radiating structure 101a in FIG. 1A) and ground plane 220 (corresponding to conductive layer 120 in FIG. 1A), indicated by electric field lines 230. This electric field is either induced through a local stimulus wherein an electrical signal is provided to radiating structure 201 through a local transmission line (that is, the microstrip antenna is used to transmit an electrical signal), or through a remote stimulus wherein radiating structure 201 is responsive to an ambient electrical signal broadcast from another electrical device (that is, the microstrip antenna element is used to receive an electrical signal).
The electric field diagram of FIG. 2 also illustrates how this electric field passes through dielectric substrate layer 210 (corresponding to dielectric substrate layer 110 in FIG. 1A), with the electric field strength at a minimum at the center of radiating structure 201 and at a maximum at the edges of radiating structure 201. These areas of maximum electric field strength (along the radiating edges of radiating structure 201) are termed the “fringing field” by those skilled in the art. The field lines of this electric field—and, by extension, the resonant frequency of the microstrip antenna element—is determined (for the most part) by the length of radiating structure 201 and the dielectric constant (or permittivity) “∈r” of dielectric substrate layer 210. The detailed methods and parameters for designing and fabricating microstrip antennas such as are illustrated in FIGS. 1A, 1B, and 2 are well known to those skilled in the art.
Previously known microstrip antenna elements are formed by providing a shaped conductive metal trace (typically copper or gold) over a dielectric substrate through industry standard lithographic techniques. However, in recent years novel methods and techniques have been introduced for forming and shaping nanotube fabric layers and films over various substrates. These nanotube fabric layers and films are conductive and can be etched (or in some cases directly formed) into specific predetermined geometries over a plurality of dielectric substances.
As described in the incorporated references, nanotube elements can be applied to a surface of a substrate through a plurality of techniques including, but not limited to, spin coating, dip coating, aerosol application, or chemical vapor deposition (CVD). Ribbons, belts, or traces made from a matted layer of nanotubes or a non-woven fabric of nanotubes can be used as electrically conductive elements. The patterned fabrics disclosed herein are referred to as traces or electrically conductive articles. In some instances, the ribbons are suspended, and in other instances they are disposed on a substrate. Numerous other applications for patterned nanotubes and patterned nanotube fabrics include, but are not limited to: memory applications, sensor applications, and photonic uses. The nanotube belt structures are believed to be easier to build at the desired levels of integration and scale (of number of devices made) and the geometries are more easily controlled. The nanotube ribbons are believed to be able to more easily carry high current densities without suffering the problems commonly experienced or expected with metal traces.
Properties of the nanotube fabric can be controlled through deposition techniques. Once deposited, the nanotube fabric layers can be patterned and converted to generate insulating fabrics.
Monolayer nanotube fabrics can be achieved through specific control of growth or application density. More nanotubes can be applied to a surface to generate thicker fabrics with less porosity. Such thick layers, up to a micron or greater, may be advantageous for applications which require lower resistance.